Mushroom coral description

Rather than forming colonies like most other corals, Fungia corals are usually solitary and generally free-living; that is, they are not attached to the substrate (except for juveniles). They are flat or dome-shaped, and either circular or elongate in outline (3). All species have wide slit-like mouths in the centre and short, tapered and widely spaced tentacles that are usually only extended at night. Very young Fungia (called acanthocauli) bear little resemblance to the adult form; they are shaped like flattened discs and are attached to the substrate via a stalk (4). Their resemblance to mushrooms gives these corals their common name.

Related species

Mushroom coral biology

Fungia corals can reproduce sexually or asexually (5). During sexual reproduction, eggs and sperm are released into the water where the egg is fertilised and develops into larvae(3). Within a fortnight, the larvae will settle on to hard substrate (5). Asexually reproduced young coral, or acanthocauli, can develop from partly buried, damaged or dying parent tissue. Either way, the result is vase-shaped polyp that gradually grows into a flattened disc, attached to the substrate via a stalk (4). The stalk of the ‘mushroom’ eventually dissolves, and the coral becomes mobile. The newly mobile coral rests on the bottom where it will mature and reproduce. The mobility of adult Fungia corals allows them to expand the reef by moving down-slope onto the soft substratum. This is an important process in reef ecosystems as it provides a hard substrate for other corals to establish and shelter for other invertebrates (4)(5).

Fungia corals are abundant on unstable substrates and in volatile environments, uninhabited by many other coral species, and are able to withstand sedimentation, breakage and immersion by freshwater for short periods of time. To survive in such environments, Fungia corals are particularly successful in their ability to repair and regenerate their tissues and skeleton. When repair is impossible, asexual reproduction allows them to repopulate an area following a catastrophe (6).

When Fungi are in immediate contact with other hard corals, they secrete a mucus that can damage coral tissues and prevents the over growth of these neighbouring corals. This mucus also plays a role in removing sediment from the coral, and facilitating in food capture (4). Fungia corals have been observed feeding on jellyfish, which may be their main food source, and is possibly the reason why these corals possess such large mouths. Occasionally, parasites reside inside the mouth; one particular parasite species, Fungiacava eilantensis, is found nowhere else in the world (4).

Species with a similar range

Mushroom coral habitat

The preferred substrates for Fungia corals are live coral and rubble, and they are more abundant on outer reef slopes than in lagoons (5). As they are free-living, and therefore readily moved by waves, Fungia are usually found below the depth of strong wave action. It is especially common on the slopes of fringing reefs where many species are usually found together (4).

Mushroom coral status

Mushroom coral threats

Fungia corals face the many threats that are impacting coral reefs globally. It is estimated that 20 percent of the world’s coral reefs have already been effectively destroyed and show no immediate prospects of recovery, and 24 percent of the world’s reefs are under imminent risk of collapse due to human pressures. These human impacts include poor land management practices that are releasing more sediment, nutrients and pollutants into the oceans and stressing the fragile reef ecosystem. Over fishing has ‘knock-on’ effects that results in the increase of macro-algae that can out-compete and smother corals, and fishing using destructive methods physically devastates the reef. A further potential threat is the increase of coral bleaching events, as a result of global climate change (7). Fungia corals may also potentially be threatened by coral harvesting. Fungia species are most popular in the dead coral trade, for use as ornaments or jewellery, rather than being traded live for aquariums. It is one of the four genera that are most frequently traded in the dead coral trade (8).

Mushroom coral conservation

Fungia corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that trade in this species should be carefully regulated (2). Indonesia and Fiji have export quotas in place for this species (2). Fungia corals will form part of the marine community in many marine protected areas (MPAs), which offer coral reefs a degree of protection, and there are many calls from non-governmental organisations for larger MPAs to ensure the persistence of these unique and fascinating ecosystems (7).

Authentication

Glossary

Asexual reproduction

Reproduction that does not involve the formation of sex cells, such as sperm and eggs. Asexual reproduction only involves one parent, and all the offspring produced by asexual reproduction are identical to one another.

Colonies

Relating to corals: corals composed of numerous genetically identical individuals (also referred to as zooids or polyps), which are produced by budding and remain physiologically connected.

Larvae

Relating to corals: the stages of development before settlement on the reef. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Polyp

Typically sedentary soft-bodied component of Cnidaria (corals, sea pens etc), which comprise of a trunk that is fixed at the base; the mouth is placed at the opposite end of the trunk, and is surrounded by tentacles.

Sexual reproduction

A form of reproduction that involves fertilization of a female cell or egg, by a male sperm. It usually involves two parents, one of either sex, but in some species individuals are hermaphrodite (possess both male and female sex organs).

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